Common language plan for speech, translate, and speech to text extensions

[picklesrus]

The speech, translate, and speaking extension blocks naturally fit together e.g.

Problem
If you choose a language that isn't supported by one of those services, the experience is pretty bad.

Proposal
Adapt the list generated for the translate extension (https://github.com/LLK/scratch-translate-extension-languages) to be a subset of all of these and use the list across all three extensions.

[ericrosenbaum]

For some reason Hebrew does not appear currently in the list of languages for the translate extension. We should remember to consider that when we do this part.